Recently, magnetic materials are applied to components of devices such as an electromagnetic wave absorber, magnetic ink and an inductance element, and an importance of the magnetic material is increased year by year. In the components, a characteristic of a magnetic permeability real part (specific magnetic permeability real part) μ′ or a magnetic permeability imaginary part (specific magnetic permeability imaginary part) μ″ of the magnetic material is utilized according to the intended use.
Patent Literature 1 discloses a core-shell magnetic material, in which a metallic fine particle is covered with an inorganic material in a multi-layered manner, as a high-frequency magnetic material.
In the magnetic material, depending on the intended use, there is a demand for a high environmental resistance in order to suppress a temporal change of the characteristic in use. Particularly, in the core-shell magnetic material, it is important to suppress oxidation of the inside (core) of the metallic fine particle.